Synthesis and Properties of a Series of Regioregularly Amino-Substituted Oligo- and Polythiophenes

Abstract

A homologous series of donor‐substituted oligothiophenes 5, 7, and 9 bearing pyrrolidino groups in the “outer” β‐positions were synthesized up to a quaterthiophene. The physical properties were investigated in dependence on the chain length of the conjugated system. Due to the substitution pattern, even the longer oligomers exhibit good film forming properties and could be electropolymerized to the corresponding donor‐substituted polythiophenes P5, P7, and P9, which promise a pure stereoregular structure. The electronic properties of both oligomers and polymers were found to be strongly dominated by the donor strength of the substituents.

Functional Oligothiophenes: Molecular Design for Multidimensional Nanoarchitectures and Their Applications

“…172 With increasing chain length of the oligothiophene, the absorption maximum was red-shifted by ∼35-50 nm compared to unsubstituted oligothiophenes, while cyclic voltammetry showed a negative shift of the oxidation potentials. Interestingly, the presence of pyrrolidino groups enhanced the electropolymerization ability of these oligothiophenes, whereas, e.g.…”

Electropolymerized Star-Shaped Benzotrithiophenes Yield π-Conjugated Hierarchical Networks with High Areal Capacitance

“…It should also be noted that the occurrence of α-β and β-β couplings in unsubstituted thiophene-based motifs subjected to oxidative polymerization conditions are known to affect conjugation, and subsequently lower the conductivity, electrochemical cycling stability, and capacitive performance of thiophene-based polymers. 33,39,40 In parallel, and as shown in Figure 3, the capacitive cycles of the several P(BTT/EDOT) copolymers (see Scheme …”

“…32,33 This oxidation onset of BTT is, however, significantly lower than that of singlering thiophene motifs (ca. +1.75 V; vs. Ag/Ag + ), 33 illustrating how redox potential depends on conjugation length and HOMO-LUMO gap reduction in more extended BTT π-systems.…”

“…33 As a result, and as previously discussed from Figure 1c, TEBTT exhibits a lower oxidation potential (E ox1 = +0.49 V). Because TEBTT is a more extended π-conjugated system, π-stacking and aggregation make it only moderately soluble in ACN, but its solubility was found sufficient in DCM (solubility up to 1.25 mM), and the later was used for the electrochemical polymerization of all TEBTT-based polymers.…”

“…+1.75 V; vs. Ag/Ag + ), 33 illustrating how redox potential depends on conjugation length and HOMO-LUMO gap reduction in more extended BTT π-systems. 33 The second and third oxidation features in the linear scan of BTT occur at E ox2 = +1.59 V and E ox3 = +2.04 V. The origin of these sequential oxidations is unclear, as those may arise from a sequential oxidation of the thiophene rings of BTT to radical cations or stem from the formation of coupled products resulting from the initial oxidation step (thiophene-based cation radicals to form oligomeric species). …”